Last December, plasma physicist Thomas Klinger saw almost 15 years of work come to life when the Wendelstein 7-X 'stellarator' — an experimental nuclear-fusion reactor — was turned on in Greifswald, Germany. The initiative had to overcome numerous challenges, but Klinger now thinks that the once-troubled project is on a solid footing.

Credit: IPP

How is plasma physics contributing to the promise of nuclear fusion?

Fusion needs a hot ionized gas known as a plasma, so basic research on high-temperature plasmas is needed for their application in fusion-based power plants. The fusion process that happens in the Sun is very difficult to realize on Earth. We must rely on magnetic fields to keep smaller fusion reactions under control.

What challenges has the Wendelstein 7-X (W7-X) stellarator faced?

When I joined the Max Planck Institute for Plasma Physics in Greifswald in 2001, the plan was to produce the first plasmas around 2007. By 2003, everybody realized that the W7-X project was in deep trouble, suffering from serious technical and management issues. The institute started to introduce reforms but they were not sufficient. So in 2005, I was put in charge of the construction project.

How did you move the W7-X project forward?

We hired an outstanding technical director and engineer, Remmelt Haange. For the first two weeks, we sat together and scratched our heads. We identified three areas to address: the most pressing technical problems; a reorganization that would involve hiring 100 engineers; and a review of the assembly plan. I got a crash course in fusion engineering. In September 2007, a new plan was accepted and a decision was made to continue the project. It was pivotal because we were in danger of being stopped.

Did you require any further skills to bring the W7-X into operation?

Our team had to learn about industrial professionalism. There are certain well-established principles, requirements and documentation practices that were not part of our management system at the institute. We had to completely reinvent ourselves.

Compare the stellarator and tokamak nuclear-fusion technologies.

Both use a magnetic field to isolate the plasma and to control its temperature. The fundamental shape of this magnetic field must be a doughnut, or a ring. In a tokamak, such as the one being built for the ITER project near Cadarache, France, the magnetic field lines are twisted into shape by inducing a strong current in the plasma. But in a stellarator such as the W7-X, there is no current in the plasma. The twisting is done by the shape of the external coils of wire. Because it doesn't need a current, the stellarator is much more stable than the tokamak, and it can operate without interruptions — desirable for a power plant. The ITER and W7-X projects are very different. ITER is an international project with seven partners on a giant machine, so its management scheme is unusual and complex compared to that of the W7-X.

Will the W7-X be competitive with ITER?

The ITER tokamak is a fantastic machine, and it still delivers the best performance. The project is far ahead. But stellarators can catch up.

What are the next steps for the W7-X?

There will be two major shutdowns in which we will integrate large and complex components into the machine to enhance its performance. After 2020, we aim to produce high-performance plasmas. Our fundamental goal is to demonstrate that these plasmas can be created and kept stable for half an hour. That would be a breakthrough, and we hope to achieve this by 2025.

Why do humans need to harness fusion?

It's the only new primary source of energy that researchers are working on, and I'm convinced that it will be needed in the long run. The quest for energy will affect everything — from water to mobility. Sufficient energy means peace.

This interview has been edited for length and clarity.